This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to a Japanese Patent Application 2001-083373 filed on Mar. 22, 2001, the entire disclosure of which is incorporated herein by reference.
The present invention generally relates to a valve timing control device. More particularly, the present invention pertains to a valve timing control device for controlling the angular phase difference between a crankshaft of a combustion engine and a camshaft of the combustion engine.
A known valve timing control device includes a rotary member which is rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the engine, a rotational transmitting member which rotates relative to the rotary member, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member to divide the pressure chamber into an advancing chamber and a retarding chamber, and a helical spring having a coil portion. A first end portion of the spring engages the rotary member and a second end portion engages the rotational transmitting member, with the spring urging the rotary member in the advancing direction to expand the advancing chamber. A controlling device supplies and discharges fluid to and from the advancing chamber and the retarding chamber to control phase alterations between the rotary member and the rotational transmitting member. An example of a known variable timing device having a construction similar to that described above is disclosed in Japanese Patent Laid-Open Publication No. Heisei 11(1999)-223112.
As a plurality of cams arranged on the camshaft push the valves of the internal combustion engine during engine operation, the rotary member always receives some force. The force rotates the rotational transmitting member in the delayed or retarding direction. The above-described known valve timing control device is provided with the helical spring to rotate the rotary member in the advancing direction so that the helical spring offsets this force. Thus, the response in the advancing direction of the rotary member is improved.
However, as shown in FIGS. 17(a) and 17(b), the structure of the helical spring 270 used in the known valve timing control device includes a coil portion 270a, a first hook portion 270b and a second hook portion 270c. The hook portion 270b engages either the rotary member or the rotational transmitting member while the hook portion 270c engages the other of the rotary member and the rotational transmitting member. Both of the hook portions 270b, 270c extend in the axial direction of the coil portion 270a. Thus, the total length (LB) of the helical spring 270 is relatively long. Therefore, the overall axial length of the known valve timing control device must be rather long.
According to one aspect, a valve timing control device includes a rotary member adapted to be rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the internal combustion engine, a rotational transmitting member rotatable relative to the rotary member, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member dividing the pressure chamber into an advancing chamber and a delaying chamber, and a helical spring which urges the rotary member in the advancing direction to expand the advancing chamber. The helical spring includes a coil portion, a first end portion engaging the rotary member and a second end portion engaging the rotational transmitting member. At least one of the first and second end portions of the helical spring extends on an imagined radial plane arranged in a radial direction of the coil portion.
According to another aspect, a valve timing control device includes a rotary member adapted to be rotatably arranged in a torque transmitting route between a crankshaft of an internal combustion engine and a camshaft of the internal combustion engine, a first annular spring space formed in the rotary member and having an inner circumferential wall and an outer circumferential wall, a rotational transmitting member rotatable relative to the rotary member, a second annular spring space formed in the rotational transmitting member and having an inner circumferential wall and an outer circumferential wall, a pressure chamber formed by the rotary member and the rotational transmitting member, a vane provided on the rotary member or the rotational transmitting member dividing the pressure chamber into an advancing chamber and a delaying chamber, and a helical spring positioned in the first and second annular spring spaces to urge the rotary member in the advancing direction to expand the advancing chamber. The helical spring includes a coil portion, a first end portion and a second end portion, with the first end portion engaging a first groove formed in one of the inner circumferential wall of the rotary member and the outer circumferential wall of the rotary member, and the second end portion engaging a second groove formed in one of the inner circumferential wall of the rotational transmitting member and the outer circumferential wall of the rotational transmitting member.